8

NJ88C50

The information contained within each word is given below.

Data bits are shifted in on the leading clock edge, with the least

significant bit(LSB) of the word first and the MSB of the word

last. (Note that individual sections of data within a word are

loaded with the MSB of that section first. An example of this

is given after this description of Word A)

Word Format

MSB...........................................LSB

Word A

|0| NF | N1

|N2 or N2 and N2+N3|

|3 bits| 12 bits |

8 bits

|

NF = Fractional-N incremental value. (MSB first)

N1 = Number of cycles prescaler ratio R1 is used. (MSB first)

N2 = Number of cycles prescaler ratio R2 is used. (MSB first)

N3 = Number of cycles prescaler ratio R3 is used. (MSB first)

If a two modulus prescaler is being used N2= 8 bits.

If a three or four modulus prescaler is being used

N2 = 4 bits and N2+N3= 4 bits(modulo-16 addition).

Therefore if the following values are required NF=3

N1=51 N2=25 the input word would be

0

110

110011000000

10011000

NF

N1

N2

Word A2

|0|

NF | N1

|N2 or N2 and N2+N3 | CN |

|3 bits | 12 bits |

8 bits

|8 bits |

CN = Scaling factor for current setting. (MSB first)

Word B

|1000 |N2+N3+N4| CN | K | L | P1,P2 |

|

4 bits

| 8 bits|4 bits|2 bits| 2 bits |

N4 = Number of cycles prescaler ratio R4 is used and

(N2+N3+N4) is modulo-16 addition. (MSB first)

CN = Scaling factor for current setting. (MSB first)

K = Acceleration factor for integral charge pump. (MSB first)

L = Acceleration factor for proportional charge pump.

(MSB first)

P1,P2 = Number of modulii of prescaler.

No. of modulii P2 P1

Two

0 0

Three

0 1

Four

1 0

Word C

|1001|

NA

|

|

| 12 bits | 8 bits free |

NA = Variable frequency for auxiliary synthesiser.

(MSB first)

Word D

|1010 | NR |SM1,SM2| DM |SA1,SA2| DA|FMOD|LONG|

|12 bits|

2 bits | 1 bit | 2 bits |1 bit| 1 bit | 1 bit |

NR = Reference frequency division value. (MSB first)

SM1,SM2 = Main reference source select (Rmain).

SM1 SM2

RMAIN

0

0

M

0

1

2M

1

0

4M

1

1

8M

SA1,SA2 = Auxiliary reference source select (Raux).

SA1 SA2

RAUX

0

0

M

0

1

2M

1

0

4M

1

1

8M

FMOD = Fractional-N modulus select (5 or 8).

FMOD MODULUS

0

5

1

8

DA = Disable auxiliary synthesiser.

DA=1-disabled

DA=0-enabled

DM = Disable main synthesiser.

DM=1-disabled

DM=0-enabled

LONG = Word A or A2 select.

LONG=0 Word A selected

LONG=1 Word A2 selected